1. Field of the Invention
The present invention relates to a fall sensor, especially to an all-directional fall sensor capable of detecting whether a product has suffered a fall or an impact
2. Description of the Related Art
Under the market demand for compact multi-functional electronics with cool design, how to prevent damages to the electronic products caused by accidental dropping is an important aspect to the design of the products. Such prevention is one of the value-added design aspects in the mechanical designs of products. Through experiments and simulations, the mechanical design is amended and shock-absorption materials are added to satisfy the specification requirement for preventing damages due to a drop. However, if during transport or within warranty a product is dropped and broken, and there is no damage readily apparent on the appearance, the maker in this case may have to bear the responsibility for fixing the product.
A buyer of a PDA or a cell phone may sometimes find the PDA or cell phone not functioning after coming home and opening the box containing the PDA or cell phone. It is usually very difficult to determine if the PDA or cell phone has suffered a fall. Sensors are normally used to determine whether the PDA or cell phone has suffered a fall or an external impact. There are a variety of sensors available, such as a capacitance sensor, a suspension spring sensor, a magnetic induction current sensor, a mass-acceleration sensor, a magnetoresistive sensor, a spring mass sensor, a piezoelectric sensor, and a fluid sensor.
U.S. Pat. No. 5,970,794 discloses a shock sensor utilizing a coil that produces a magnetic field. The magnetic field changes when there is a shock and the sensor outputs an induced electric current.
U.S. Pat. No. 5,983,724 discloses a shock sensor that contains a magnetic shock-sensing member rotatably disposed in the sensor. When there is shock, the magnetic shock-sensing member rotates and outputs a signal caused by a magnetoresistive effect.
U.S. Pat. No. 5,575,479 discloses a projectile impact indicating target. When the projectile is hit, an impact indicator is released from the projectile.
Taiwan Patent No. I 255342 discloses a shock sensor comprising a spring plate apparatus disposed inside a cell phone. The spring plate apparatus comprises two spring plates that are connected together and have electrical currents passing through. When the cell phone suffers a fall or an impact, one of the spring plates disconnects with the other and turns off the electrical current.
Shock Watch Company produces a shock indicator model no. MAG2000. The shock indicator is for placing on the container used for transporting products or machines. The indicator is basically a casing with two rooms. A magnet is placed in the center of one room, and a magnetic material is movably placed in another room. The impact direction and the magnetic field line generated between the magnet and the magnetic material are perpendicular. The magnetic material is attracted to the magnet, and when the indicator suffers a drop or an impact, the magnetic material moves towards the direction of the impact or fall; whether the container has suffered a fall or an impact can thus be determined.